In recent years, various types of image pickup module in which solid-state image sensing devices are used as image pickup devices have been developed to be mounted into digital cameras, digital video units, etc. Examples of solid-state image sensing devices here encompass solid-state image sensing devices each constituted by a CCD (charge-coupled device) and a CMOS (complementary metal-oxide semiconductor), etc. Use of such solid-state image sensing devices makes it possible to constitute image pickup modules that are small in size and low in height.
In particular, portable terminals such as portable information terminals and portable phones have spread rapidly in recent years. Image pickup modules that are mounted into such portable terminals are required to include image pickup lenses that are high in resolving power, small in size, and low in height.
As an example of an image pickup lens that is high in resolving power, small in size, and low in height, Patent Literature 1 discloses an image pickup lens (so-called telescopic image pickup lens) constituted by using two lenses, namely a first lens having a positive refracting power and a second lens having a negative refracting power.
Because the whole length of the image pickup lens disclosed in Patent Literature 1 is shorter than the focal length of the image pickup lens as a whole, the image pickup lens can be small in size and low in height. Further, because the first and second lenses of the image pickup lens disclosed in Patent Literature 1 combine to correct various aberrations such as coma aberrations, astigmatism, and field curvatures, the image pickup lens can be high in resolving power. Therefore, the technique disclosed in Patent Literature 1 makes it possible to realize a small-size image pickup lens satisfactory in optical characteristic.
Further, as another example of an image pickup lens that is high in resolving power, small in size, and low in height, Patent Literature 2 discloses an image pickup lens constituted by using two lenses, namely a first lens having a positive refracting power and a second lens having a positive or negative refracting power.
As other examples of image pickup lenses that are high in resolving power, small in size, and low in height, there are image pickup lenses each constituted by using two lenses, namely a first lens having a positive refracting power and a second lens having a positive refracting power (see Patent Literatures 4 to 7 and 9 to 11).
It should be noted that Patent Literature 3 discloses a wide-angle lens for camera which maintains a high resolving power and which can be easily manufactured.
The lens disclosed in Patent Literature 3 is constituted by using two lenses, namely a first lens having a positive or negative refracting power and a second lens having a positive refracting power. Furthermore, the lens disclosed in Patent Literature 3 is intended to have spherical aberrations and field curvatures remedied by curving a film constituting an image surface.
Each of the techniques disclosed in Patent Literatures 1 to 11 realizes a small-size, low-height image pickup lens by shaping each of its first and second lenses so that each of those surfaces of the lens which face an object and the image surface, respectively, includes a concave surface and/or a convex surface.